inter-chip and intra-chip Harm Dorren and Oded Raz

Transcription

1 Will photonics penetrate into inter-chip and intra-chip communications? Harm Dorren and Oded Raz

2 On-chip interconnect networks R X R X R X R X R T X R XT X T X T X T X X Electronic on-chip interconnect network Interconnect needs repeaters Each repeater receive, buffers and re-transmits every bit Higher clock frequencies: more power per repeater and more repeaters T X Networking R X Optical on-chip interconnect network No repeaters Power independent d of distance/ no cross talk, etc Forecast for 2020 Photo by IBM 10 TFLOP processors On-chip I/O ~ 1 byte per flop (Amdahl) Power electronic network 10 TFLOPs chip ~ 500 Watts ~ 7 pj/bit or 7 mw/gb/s PAGE 2

3 Photonic interconnect network: Receiver Transmission path Receiver Transmitter Interconnect plane Processor plane Typical receiver sensitivity at BER 10-9 PIN APD Power (TIA) 40 Gb/s -10 dbm - ~ 250 mw 10 Gb/s -20 dbm - 25 dbm ~200 mw 2.5 Gb/s -25 dbm -30 dbm ~75 mw PAGE 3

4 Photonic interconnect network Transmission path Transmission path Receiver Transmitter Typical waveguide losses Typical losses Bending radius Silica 001dB/cm micrometer Etchless silicon 0.3 db/cm 50 micrometer SOI 2.4 db/cm 5 micrometer InP membranes 3 db/cm 5 micrometer PAGE 4

5 Photonic Interconnect network: Option 1: Off-chip laser and transmitter Laser Modulator Transmission path Receiver Coupling losses (3dB) Power laser Power modulator Power modulator driver Insertion losses 40 Gb/s 150 mw 60 mw 5.85 W 8 db 10 Gb/s 150 mw < 50 mw 3.6 W 8 db 2.5 Gb/s 150 mw < 50 mw 1~2 W 8 db Silicon modulators, MZI or Ring resonator, limited data available, but high losses, and high power! /Department of See Electrical Ding Engineering and Pan, SLIP PAGE 5

6 Direct modulation Use microdisk laser (diameter 7.5 micrometer) Threshold current is ~ 0.1 ma Power 5 mw (2V, 2.5mAmps) Optical power in waveguide ~ 50 mw 10 Gb/s wavelength conversion is possible but direct modulation at high speed never been demonstrated Devices made by IMEC/Gent (FP7 project HISTORC) PAGE 6

7 Link and power budget 40 Gb/s (off-chip laser) Receiver sensitivity (PIN): -10 dbm Waveguide losses: 5 db Insertion losses modulator: 8 db Coupling losses 3 db Required laser power 6 dbm (4mW) Power laser Power modulator Power modulator driver Power TIA Receiver: 150 mw 60 mw 210 mw (5.25 mw/gb/s) 5850 mw 250 mw 6100 mw (153 mw/gb/s) PAGE 7

8 Link and power budget 10 Gb/s (off-chip laser) Receiver sensitivity (APD): - 25 dbm Waveguide losses: 5 db Insertion losses modulator: 8 db Coupling losses 3 db Required laser power -9 dbm (0.13 mw) Power laser Power modulator Power modulator driver Power TIA Receiver: 150 mw 50 mw 200 mw (20 mw/gb/s) 3600 mw 200 mw 3800 mw (380 mw/gb/s) PAGE 8

9 Link and power budget 25Gb/s (off-chip laser) 2.5 Gb/s (off-chip laser) Receiver sensitivity (APD): - 30 dbm Waveguide losses: 5 db Insertion losses modulator: 8 db Coupling losses 3 db Required laser power -14 dbm (0.04 mw) Power laser Power modulator Power modulator driver Power TIA Receiver: 150 mw 50 mw 200 mw (80 mw/gb/s) 1000 mw 75 mw 1075 mw (430 mw/gb/s) PAGE 9

10 Link and power budget 2.5 Gb/s (direct modulation) Receiver sensitivity (APD): - 30 dbm Waveguide losses: 5 db Insertion losses modulator: 8 db Coupling losses 3 db Required laser power -14 dbm (0.04 mw) Power laser Power modulator Power modulator driver Power TIA Receiver: 5 mw 0 mw 5 mw (2 mw/gb/s) 0 mw 75 mw 75 mw (30 mw/gb/s) PAGE 10

11 Bandwidth distance product including driver power Off-chip laser at 2.5, 10 and 40 Gb/s ower (mw W) P Electronic with repeaters (3.5 GHz) Direct modulation at 2.5 Gb/s Distance (mm) PAGE 11

12 Bandwidth distance product without driver power Off-chip laser at and 40 Gb/s Power (m mw) 10 Electronic with repeaters (3.5 GHz) Direct modulation at 2.5 Gb/s distance (mm) PAGE 12

13 Conclusions (1) Off-chip laser - Sufficient link budget to allow some networking, but,.. high power dominated by drivers On-chip laser - Sufficient i power for a single link, but,. insufficient link budget for a network on a chip PAGE 13

14 Conclusions (2) Photonics gives an improved bandwidth distance product: Bandwidth is limited it by electronics, thus photonics only gives distance!!! Need applications with distance PAGE 14